Advances in Recycling of Thermoplastics and Fiber-Reinforced Thermosetting Composites: Overview of West Virginia Approaches

n this presentation, I will introduce the future development of chemical recycling as an initiative to solve the plastic problem.　In particular, I will introduce the outline of the actual chemical recycling process and explain the necessity of fusion of the arterial industry and the venous industry for the future based on the case of the technological development.

Integration of arterial and venous industries & promotion of chemical (feedstock) recycling

Chitin is the second most abundant biopolymer, after cellulose. It is present in the shell of crustaceans, in the cuticle of insect and even in some fungi. Chitin can be converted into chitosan, a highly praised material in the biomedical sector for its antibacterial properties, which finds also important application as a fertilizer, water treatment flocculant and food additive. Yet today's technologies for chitosan production from biomass rely on the use of corrosive treatments, high energy input and large quantities of by product effluents. Herein we are presenting our group's effort to tackle this question. We showed that mechanochemistry and aging could be used effectively for the deacetylation of chitin.1 This process yielded high molecular weight chitosan with minimal use of energy and solvent. This method is versatile and applicable to a number of chitin sources, including crude crustacean and insect shells, yielding deacetylation up to 98% and remarkably high molecular weights. This process affords chitosan in a safer fashion and with less materials and energy usage compared to the classic hydrothermal one. We have also extended this method to the fabrication of chitosan nanocrystals from chitin nanocrystals.2 Chitin and chitosan nanocrystals featured enhanced properties are nanocatalysts supports.3,4 We have also developed hydrogels from chitosan and chitin nanocrystals, with exceptional gelling properties and demonstrated their applicability for slow drug release.

Upcycling biomass: from crustacean waste to functional materials

Composites, and especially carbon fibre reinforced plastics (CFRP), have impressively demonstrated their mechanical performance in several applications in the last years, starting from aerospace, finding their way into sports and commodities and just recently having a significant increase in the wind energy sector. These materials are often referred to as “a material with high potential”. The question is: potential to what? The potential to be a solution to the CO2-problem due to lightweight construction capabilities and the possibility to contribute to fuel savings during the lifetime of an aircraft, a truck or a car, to provide clean energy with more efficient next-gen wind turbines? Or is it the potential to be part of the problem, as the material is very difficult to recycle and currently causes trouble in waste incineration plants and in many cases just ends up in landfills. The presented talk will address the state of the art of recycling CFRP-materials: in a first step the different components of the materials (fibres and plastics, the so called matrix) need to be separated. This can be done via pyrolysis on a commercial scale, or by different alternatives with lower TRL levels. After that the recovered fibres are processed into semi-finished products, such as nonwovens, that are suitable to replace the first-gen materials in terms of handling and processing. All along the way, it is necessary to monitor the properties of the materials, in order to be able to identify correlations of process-parameters and resulting properties, both for quality assurance in a future supply chain, as well as identification of further demand for continuing R&D-activities. Finally, the stakeholders in a circular economy are adressed: why should a company invest in the improvement of recycle-ability of their products? This discussion is not limited to CFRP-materials only, but is open to interaction with other material classes with emerging circularity.

Recycling of fibre reinforced plastics - state of the art and outlook

1) Traditional Thermosets:
Excellent mechanical strength,
Thermal stability,
Solvent resistance.
2) Vitrimers (recyclable thermosets)
Excellent mechanical strength,
Good recyclability
Self-healing and repairing

Catalyst-Free Epoxy Vitrimer for Recyclable and Self-Healing Solid Polymer Electrolytes

Our group has optimised and performed the pyrolysis of PE, PP and PS plastics alongside 2 commonly found waste plastic with good conversion rates and selectivity. The incineration ash and pyrolysis oil generated will be characterised and attempts will be made to functionalise them into specialty chemicals. 

Catalytic pyrolysis of plastic waste with incineration fly ash into fuels for upcycling

Flexible electronics are of critical importance for medical devices, portable electronics, smart textiles, energy storage, communication and sensor systems [1,2]. However, the lifetime of electronics is becoming shorter, which poses a growing ecological problem. Therefore, it is urgent and necessary to find sustainable and cost-efficient materials to replace the crude oil-derived polymers that are commonly used in flexible electronics. To this end, fish gelatin (FG) extracted from fish scales could provide an eco-friendly and biodegradable alternative to plastic for use in flexible electronics. Fish scales are inedible and malodorous kitchen waste, and >2 million metric tons of fish scales are discarded each year. This talk will introduce our recent works on FG-based flexible electronics, including flexible electroluminescent devices and triboelectric nanogenerators (TENGs) [3-6]. The properties of FG films, the structure design and the performance of flexible electronic devices will be briefly discussed. These works may pave a new way to green and sustainable flexible electronics.

References
1. S. Xu, A. Jayaraman, J. A. Rogers. Skin sensors are the future of health care. Nature, 2019, 571, 319-321.
2. G.-H. Lee, H. Moon, H. Kim, G. H. Lee, W. Kwon, S. Yoo, D. Myung, S. H. Yun, Z. Bao, S. K. Hahn. Multifunctional materials for implantable and wearable photonic healthcare devices. Nat. Rev. Mater., 2020, 5, 149–165.
3. X. P. Zhang, T. Y. Ye, X. H. Meng, Z. H. Tian, L. H. Pang, Y. J. Han, H. Li, G. Lu, F. Xiu, H. D. Yu, J. Q. Liu, W. Huang. Sustainable and transparent fish gelatin films for flexible electroluminescent devices. ACS Nano, 2020, 14, 3876-3884.
4. T. F. Jiang, X. H. Meng, Z. Zhou, Y. Y. Wu, Z. H. Tian, Z. D. Liu, G. Lu, M. Eginlidil, H. D. Yu, J. Q. Liu, W. Huang. Highly flexible and degradable memory electronics comprised of all-biocompatible materials. Nanoscale, 2021, 13, 724-729.
5. Y. J. Han, Y. F. Han, X. P. Zhang, G. Lu, H. D. Yu, W. Huang. Fish gelatin-based triboelectric nanogenerator for harvesting biomechanical energy and self-powered sensing of human physiological signals. ACS Appl. Mater. Interfaces, 2020, 12, 16442-16450.
6. Q. Z. Sun, H. C. Wang, L. Wang, X. P. Yue, L. R. Zhang, G. Z. Ren, D. H. Li, Y. J. Han, L. L. Xiao, G. Lu, H. D. Yu, W. Huang. Fully sustainable and high-performance fish gelatin-based triboelectric nanogenerator for wearable movement sensing and human-machine interaction. Nano Energy, in revision.

Sustainable Flexible Electronics Based on Fish Gelatin

The recent trends in rare-earth usage and applications are discussed. Most of the motors of electric cars use Neodymium-iron-boron magnets, resulting in 1-2 kg of NdFeB magnets per vehicle. This can push significantly the demand for NdFeB magnets. Other application that may increase the demand of NdFeB magnets are giant off-shore wind turbines. The production of light rare-earths as neodymium and praseodymium can be easily increased. However, heavy rare-earths as terbium and dysprosium are scarce, and its price has increased significantly. Many Brazilian projects are stopped in present moment, waiting cheaper methods of rare-earth separation. However, Serra Verde project (state of Goias - Brazil) was scheduled to start in 2022. Recycling should be an economical activity. This explain why the recycling of rare-earths at the present time is very small. The recycling of rare-earths is estimated to be around 1% or less. The re-use of magnets is a possibility. This can be viable only since there is a standardization of manufactured magnets. 


Influence of grain size in the coercivity of sintered magnets

This poster is on the use of the HPMS process (Hydorgen processing of magnet scrap) to liberate NdFeB alloy powders from water pumps, wind turbine magnets and loudspeakers. The separated powder has been subsequently processed into HDDR powders. The HDDR microstructures and magnetic properties are reported here.

HPMS Optimisation for End of Life NdFeB Containing Products

We are investigating the novel possibilities and aspects of electrochemical recycling and reprocessing of Nd-Fe-(B)-based and Sm-Co magnets. First, we investigated the possibility of electrodeposition of Nd-Fe alloy at room T from ionic liquid based on 1-ethyl-3-methylimidizolium dicyanamide ([EMIM][DCA]) [1]. The electrodeposition of the rare earths (REs) at room T, is still a challenge because of their extremely low electrochemical potential. We observed that Nd(III) cannot be reduced independently, but it can be co-deposited with the addition of Fe(II). Further, we propose [2] a new concept of recycling the sintered (Dy,Nd)-Fe-B magnets selective electrochemical etching recovering the 2:14:1 matrix phase. Via an electrochemical etching method, we are able to recover pure individual 2:14:1 grains that can be re-used for new types of magnet production. Similar anodic etching was applied also for Sm-Co magnets, where it was shown, that it is possible to selectively etch the Sm, with simultaneous deposition of Co, Fe, and Cu on the cathode. With regards to the energy consumption of the new process, the proposed route is comparable to the established direct re-use methods like remelting and hydrogen processing of magnetic scrap. Further to tackle the issue of efficient and environmentally friendly rare earth recycling, we propose a novel electrochemical method for Nd–Fe–B PMs etching and REs recycling [3]. The proposed procedure enables complete electrochemical etching of the Nd–Fe–B magnet with further selective REs recovery and a simultaneous Fe metal deposition. The proposed procedure thus avoids the formation of solid Fe-based waste with the total re-use of the electrolyte resulting in no wastewater discharge.

Electrochemical Recycling and Reprocessing Aspects of Rare Earth-based Permanent Magnets

NdFeB magnet waste flows in the light of recycling – A detailed assessment

This paper investigates the viability of hydrogen decrepitation as a means for recovery and recycling of samarium cobalt (SmCo5) magnets. To hydrogen decrepitate SmCo5, a higher pressure is required compared to the atmospheric pressure used for NdFeB magnets, but it is essential to find the lowest energy route to make it economically viable. Samples of SmCo5 were characterised using scanning electron microscopy and X-ray diffraction (XRD), before using intelligent gravimetric analysis (IGA) to determine the hydrogen absorption plateau pressures at a range of temperatures. The samples were then subjected to a range of pressures from 5-20 bar, as well as a high temperature and pressure trial at 300 ⁰C and 20 bar, to find the conditions at which the magnets broke down into powders. IGA measurements showed that increasing the reaction temperature also increased the plateau pressure for absorption, and that the plateau pressure at room temperature was ~6 bar. Magnetised bulk samples of SmCo5, however did not react at this plateau pressure, instead requiring a minimum 10 pressure bar at room temperature over 24 hours, however they did not demagnetise. Recommendations were made to improve the viability of hydrogen decrepitation for recovery and recycling of SmCo5 magnets.


Underline digital video library

Advances in Recycling of Thermoplastics and Fiber-Reinforced Thermosetting Composites: Overview of West Virginia Approaches

Integration of arterial and venous industries & promotion of chemical (feedstock) recycling

Upcycling biomass: from crustacean waste to functional materials

Recycling of fibre reinforced plastics - state of the art and outlook

Catalyst-Free Epoxy Vitrimer for Recyclable and Self-Healing Solid Polymer Electrolytes

Catalytic pyrolysis of plastic waste with incineration fly ash into fuels for upcycling

Sustainable Flexible Electronics Based on Fish Gelatin

Influence of grain size in the coercivity of sintered magnets

HPMS Optimisation for End of Life NdFeB Containing Products

Electrochemical Recycling and Reprocessing Aspects of Rare Earth-based Permanent Magnets

NdFeB magnet waste flows in the light of recycling – A detailed assessment

Recovery and Recycling of SmCo5 Using Hydrogen Decrepitation

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